Systems and methods for indicating an amount of use of a sensor

ABSTRACT

Aspects of the present disclosure include systems and methods for indicating an amount of use of a pulse oximetry sensor. According to one embodiment, the system includes an oximeter that monitors the amount of use for a given sensor. The oximeter and/or the sensor may advantageously include a visual alarm, an audio alarm, a vibrational alarm, a power down function, or the like, which can be activated when a predetermined amount of use has expired. According to another embodiment, the system includes a sensor having a memory device storing a unique identifier.

REFERENCE TO RELATED APPLICATION

The present application claims priority benefit under 35 U.S.C. §120 toand is a continuation of U.S. patent application Ser. No. 11/714,303,filed Mar. 6, 2007, entitled “Systems and Methods for Indicating anAmount of Use of a Sensor,” now U.S. Pat. No. 7,910,875, which is acontinuation of U.S. patent application Ser. No. 11/311,212, filed Dec.19, 2005, entitled “Amount of Use Tracking Device and Method for MedicalProduct,” now U.S. Pat. No. 7,186,966, which is a continuation of U.S.patent application Ser. No. 11/065,994, filed Feb. 24, 2005, entitled“Systems and Methods for Indicating an Amount of Use of a Sensor,” nowU.S. Pat. No. 6,979,812, which is a continuation of U.S. patentapplication Ser. No. 10/357,531, filed Feb. 3, 2003, entitled “Systemsand Methods for Indicating an Amount of Use of a Sensor,” now U.S. Pat.No. 6,861,639, which is a continuation of U.S. patent application Ser.No. 09/502,032, filed Feb. 10, 2000, entitled “A System for Indicatingthe Expiration of the Useful Operating Life of a Pulse Oximetry Sensor,”now U.S. Pat. No. 6,515,273, which is a continuation-in-part of U.S.patent application Ser. No. 09/420,544, filed Oct. 19, 1999, entitled“Shielded Optical Probe and Method,” now U.S. Pat. No. 6,580,086, whichclaimed a priority benefit under 35 U.S.C. §119(e) to U.S. ProvisionalPatent Application Ser. No. 60/150,922, filed Aug. 26, 1999, by the sametitle. The present application incorporates the foregoing disclosuresherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention in general relates to sensors for measuring oxygencontent in the blood, and, in particular, relates to an apparatus andmethod for monitoring the life of a pulse oximetry sensor.

2. Background

Early detection of low blood oxygen is critical in a wide variety ofmedical applications. For example, when a patient receives aninsufficient supply of oxygen in critical care and surgicalapplications, brain damage and death can result in just a matter ofminutes. Because of this danger, the medical industry developed pulseoximetry, a noninvasive procedure for measuring the oxygen saturation ofthe blood. A pulse oximeter interprets signals from a sensor attached toa patient in order to determine that patient's blood oxygen saturation.

A conventional pulse oximetry sensor has a red emitter, an infraredemitter, and a photodiode detector. The sensor is typically attached toa patient's finger, earlobe, or foot. For a finger, the sensor isconfigured so that the emitters project light from one side of thefinger, through the outer tissue of the finger, and into the bloodvessels and capillaries contained inside. The photodiode is positionedat the opposite side of the finger to detect the emitted light as itemerges from the outer tissues of the finger. The photodiode generates asignal based on the emitted light and relays that signal to the pulseoximeter. The pulse oximeter determines blood oxygen saturation bycomputing the differential absorption by the arterial blood of the twowavelengths (red and infrared) emitted by the sensor.

The foregoing conventional sensor is typically detachable from theoximeter to allow for periodic replacement. Periodic replacement isadvantageous for a wide variety of reasons. For example, the sensor canbecome soiled, thereby possibly inhibiting sensor sensitivity or causingcross-patient contamination. Furthermore, the electronic circuitry inthe sensor can become damaged, thereby causing sensor failure orinaccurate results. Moreover, the securing mechanism for the sensor,such as an adhesive substrate, can begin to fail, thereby improperlypositioning the sensor in proximity to a measurement site and providinginaccurate data. Accordingly, periodic replacement of the sensor is animportant aspect of maintaining a sterile, highly sensitive, accuratepulse oximetry system.

However, a conventional pulse oximetry sensor is wholly reliant on anoperator for timely replacement of soiled, damaged, or otherwiseoverused sensors. This approach is problematic not only from thestandpoint of operator mistake or negligence, but also from theperspective of deliberate misuse for cost saving or other purposes.

Based on the foregoing, significant drawbacks exist in the reliance onthe operator for the periodic replacement of conventional pulse oximetrysensors. Accordingly, a need exists for a pulse oximetry sensor havingthe ability to monitor its own usable life.

SUMMARY OF THE INVENTION

Accordingly, one aspect of the present invention is to provide aninexpensive, highly accurate sensor life monitoring system formonitoring the useful and safe life of a pulse oximetry sensor.According to one embodiment, the sensor life monitoring system includesa timer and a sensor life indicator. According to another embodiment,the timer includes a divide-by-n counter and a non-volatile RAM, whilethe sensor life indicator includes at least one LED or incandescentbulb.

Therefore, one aspect of the present invention is a pulse oximetrysensor comprising a drive connection carrying a drive signal, whereinthe drive signal has pulses. The pulse oximetry sensor further comprisesa timer connected to the drive connection and configured to generate atimer output signal after a predetermined number of pulses are generatedin the drive signal; and a sensor life indicator connected to the timeroutput signal and configured to provide an indication when the timeroutput signal is generated. The pulse oximetry sensor further comprisesan LED network connected to the drive connection and configured toproject light through a measurement site when pulsed by the drivesignal; and a photodetector configured to detect the projected light andoutput a signal representative of constituents or characteristics of themeasurement site.

Another aspect of the present invention is a sensor life monitoringsystem comprising a timer connected to a sensor drive signal; and asensor life indicator connected to the timer such that the sensor lifeindicator is configured to indicate the expiration of the useful or safelife of a pulse oximetry sensor.

Another aspect of the present invention is a pulse oximetry system thatcomprises a pulse oximeter; a sensor connected to the pulse oximeter;and a sensor life monitor connected to the sensor and configured tomonitor the useful and safe life of the sensor.

Another aspect of the present invention is a method of manufacturing asensor. The method comprises connecting a timer to one of a sensor inputand a sensor output; and connecting an indicator to the timer such thatwhen the timer expires, the indicator is activated.

Another aspect of the present invention is a method for monitoring thelife of an oximetry sensor. The method comprises monitoring a parameterresponsive to repeated use of a sensor. When the parameter indicatesthat the sensor has expired, the method generates an expirationindication.

Another aspect of the present invention is an oximetry sensor lifeindicator that comprises a non-volatile counter connected to receive adrive signal having a plurality of transitions where the counter changesa count value in response to the transitions. The oximetry sensor lifeindicator further includes a sensible indicia connected to the counter,where the sensible indicia has a first state, and a second state and thesensible indicia changes from the first state to the second state toindicate the end of life of the oximetry sensor when the count value inthe counter reaches a predetermined value.

Another aspect of the present invention is an oximetry system comprisingan oximeter; a sensor attached to the oximeter through a cable; a timerconnected to at least one of a sensor drive signal and a sensor returnsignal; and a sensor life indicator connected to the timer.

Another aspect of the present invention is an oximetry system comprisinga sensor having a timer, wherein the timer produces a sensor expirationsignal. An oximeter is connected to the sensor and is configured toreceive the sensor expiration signal from the timer.

Another aspect of the present invention is an oximetry system comprisinga sensor having a reset indicator. An oximeter is connected to thesensor and is configured to monitor whether the reset indicator has beenset.

Another aspect of the present invention is a pulse oximetry systemcomprising a pulse oximeter and a sensor connected to the pulseoximeter. The sensor is adapted to measure a physiological parameter.The pulse oximetry system also comprises a memory device connected tothe sensor and adapted to measure the useful life of the sensor.

Another aspect of the present invention is a pulse oximetry systemcomprising a sensor having an emitter, a detector, and a memory devicestoring a characteristic of the sensor. The pulse oximetry system alsocomprises a pulse oximeter connected to the sensor and adapted to readthe characteristic of the sensor and the output of the detector. Thepulse oximetry system also comprises a database connected to the pulseoximeter and adapted to store the characteristic along with a longevitymeasurement corresponding to the sensor.

For the purposes of summarizing the invention, certain aspects,advantages, and novel features of the invention have been described. Ofcourse, it is to be understood that not necessarily all such advantagesmay be achieved in accordance with any particular embodiment of theinvention. Thus, the invention may be embodied or carried out in amanner that achieves or optimizes one advantage or a group ofadvantages, as taught herein, without necessarily achieving otheradvantages as may be taught or suggested herein.

Other aspects and advantages of the invention will be apparent from thedetailed description below and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in more detail below in connectionwith the attached drawings, which are meant to illustrate and not limitthe invention, and in which:

FIG. 1 illustrates a block diagram of a typical oximetry system;

FIG. 2 illustrates a block diagram of a sensor life monitoring systemaccording to an embodiment of the invention;

FIG. 3 illustrates a block diagram of the sensor life monitoring systemof FIG. 2, according to another embodiment of the invention;

FIG. 4 illustrates a block diagram of an oximetry system having a sensorlife monitoring system, according to yet another embodiment of theinvention;

FIG. 5 illustrates a block diagram of an oximetry system having a sensorlife monitoring system, according to yet another embodiment of theinvention;

FIG. 6 illustrates a flow diagram of the operation of a microprocessorof the oximetry system of FIG. 5;

FIG. 7 illustrates a block diagram of an oximetry system having a sensorlife monitoring system, according to yet another embodiment of theinvention; and

FIG. 8 illustrates a block diagram of an oximetry system having a sensorlife monitoring system, according to yet another embodiment of theinvention.

DETAILED DESCRIPTION

The inventions are described in detail below with reference to thefigures, wherein like elements are referenced with like numeralsthroughout.

FIG. 1 illustrates a block diagram of a typical oximetry system 100 usedto determine arterial oxygen saturation. The oximetry system 100includes an oximeter 105 and a sensor 110 connected to the oximeter 105via a patient cable 115. The oximeter 105 includes a microprocessor (pp)120, a speaker 125 and a display 130. The sensor 110 includes a driveconnection 135 connected to at least one LED network 140, a photodetector 145 connected to a return signal connection 150, and a cableconnector 155 housing one end of each of the drive connection 135 andthe return signal connection 150. As mentioned, the sensor 110 attachesto the oximeter 105 via the patient cable 115. The patient cable 115includes a sensor connector 160 for electrically mating with the cableconnector 155 of the sensor 110.

As previously mentioned, the typical oximetry system 100 produces adrive signal and transmits the drive signal through the patient cable115 and the drive connection 135 to the LED network 140 such that lightenergy is transmitted from the LED network 140 through tissue. The photodetector 145 senses the light energy, which has now been attenuated bythe blood in tissue, and sends a representative signal of the lightenergy back to the oximeter 105 through the return signal connection 150and the patient cable 115. The oximeter 105 analyzes the representativesignal from the photo detector 145 to determine constituence andcharacteristics of the blood in the tissue.

The sensor 110 typically includes the foregoing electronic circuitry andan attachment mechanism formed to secure the electronic circuitry to ameasurement site. The sensor 110 may be disposable, wherein theattachment mechanism is likely formed from an adhesive structure.Moreover, the sensor 110 may be reusable, wherein the attachmentmechanism is likely formed from a clip-on structure. Also, the sensor110 may be a combination of the disposable and reusable type sensors,wherein a disposable attachment mechanism removably attaches theelectronic circuitry such that the electronic circuitry is reusable.Furthermore, the sensor 110 may include an information elementelectrically connected to the LED network 140. Such an informationelement advantageously provides quality control, security, andidentification functions.

An example of the combination sensor having an information elementdistributed in the disposable attachment mechanism is described in U.S.patent application Ser. No. 09/456,666, filed on Dec. 9, 1999, titled,“Resposable Pulse Oximetry Sensor,” assigned to the assignee of thecurrent application, and incorporated by reference herein.

FIG. 2 illustrates a block diagram of a pulse oximetry sensor 200,according to an embodiment of the invention. As shown in FIG. 2, thesensor 200 includes a wholly incorporated sensor life monitoring system203. The sensor life monitoring system 203 includes a timer 205 and asensor life indicator (SLI) 210. According to this embodiment, the timer205 is electrically connected to the drive connection 135 such that thetimer 205 also receives the drive signal from the oximeter 105. Thetimer 205 also connects to the sensor life indicator 210.

As the oximeter 105 drives the LED network 140, the timer 205 monitorsthe number of drive pulses produced and keeps a running count. After theoximeter 105 produces a predetermined number of drive signals, the timer205 provides a signal to the sensor life indicator 210, such that thesensor life indicator 210 produces an indication that the sensor 200 hasexpired and should be replaced.

FIG. 3 illustrates a block diagram of an example of the sensor lifemonitoring system 203 of FIG. 2, according to one embodiment of theinvention. As shown in FIG. 3, the timer 205 advantageously comprises anon-volatile counter. One embodiment of the non-volatile counteradvantageously comprises a counter 300 having an output that connects toan input of a logic gate 302. An output of the logic gate 302 connectsto an adder 304. As used herein, an “adder” can be an arithmetic unit,which may also be implemented as a subtractor or the like. The adder 304connects to a non-volatile (NV) RAM 305 (A non-volatile RAM does notlose data when the power is turned off or otherwise terminated). Anoutput of the NVRAM 305 reconnects as feedback to the adder 304. Also,an output of the most significant bit (MSB) of the NVRAM 305 connects toboth an inverter 307 and the sensor life indicator 210. The inverter 307connects as feedback to another input of the logic gate 302. Moreover,the output of the logic gate 302 activates or clocks the NVRAM 305.

According to one embodiment, the counter 300 comprises a divide-by-ncounter, producing an incremental output count only after n inputpulses, or transitions, of the drive signal. Using a divide-by-n counteradvantageously reduces the capacity requirements of the NVRAM 305.Furthermore, according to one embodiment, the logic gate 302 is an ANDgate, the adder 304 is a plus-one adder. Thus, each time the adder 304receives an input, it adds one to the current count stored in the NVRAM305. According to one embodiment, the NVRAM 305 is a seventeen-bitnon-volatile memory that clocks, for example, on the trailing edge ofthe output of the logic gate 302.

According to an embodiment of the invention, the sensor life indicator210 comprises a sensible indicia, such as visible light. For example,the sensible indicia may advantageously be an LED 310, or the like.Alternatively, the sensible indicia may be audible, vibrational, a powerdown of the sensor 200 or the oximeter 105, or the like.

The operation of the foregoing timer 205 and sensor life indicator 210will be disclosed with reference to two differing time frames. The firsttime frame refers to when a new sensor 200 is initially attached to theoximeter 105 and provided with a drive signal. The second time framerefers to when the sensor 200 has previously been used, and a new drivesignal is applied.

First Use of the Sensor 200

According to the foregoing embodiment, the sensor life monitoring system203 initially functions as follows. The oximeter 105 outputs a drivesignal at, for example, one kHz. The counter 300 comprises adivide-by-1000 counter that advantageously produces, for example, anoutput only after one thousand cycles of the drive signal, or every onesecond. Furthermore, assuming the count stored in the NVRAM 305 isinitially zero, the output of the MSB of the NVRAM 305 is zero. Theinverter 307 inverts the output of the MSB such that the logic gate 302passes the output of the counter 300 to the adder 304. Thus, accordingto this example, the adder 304 receives a pulse every second from thecounter 300. With each pulse, the adder 304 adds one to count stored inthe NVRAM 305. Thus, after one second, the adder 304 places a one in theNVRAM 305. After another second, the adder 304 places a two in the NVRAM305, and so forth until the NVRAM 305 fills to capacity, or the oximeter105 ceases producing the drive signal. Both events are further discussedas follows.

Subsequent Use of the Sensor 200

When the oximeter 105 sends pulses to a previously used sensor 200, theNVRAM 305 will already have a previous count stored therein. Theprevious count is loaded into the adder 304 such that as the logic gate302 outputs the foregoing signal every second, the adder 304 adds one tothe previous count. For example, if the previous count were one hour, or3,600 seconds, the first pulse received by the adder 304 from thecounter 300 will store 3,601 in the NVRAM 305. Thus, much like anautomobile odometer, the NVRAM 305 stores a running count, or times, theused life of the sensor 200.

When the count stored in the NVRAM 305 reaches capacity (in other words,sets the MSB), the output of the MSB switches. Therefore, the output ofthe inverter 307 switches such that the logic gate 302 blocks any futuresignals output from the counter 300 from reaching the adder 304.Moreover, the output of the MSB further activates the LED 310 such thatthe LED 310 indicates the sensor 200 has expired. This indication by theLED 310 signals the operator to replace the used sensor 200 with a newone. The indication advantageously provides multiple people with theknowledge that the sensor 200 should be changed. For example, doctors,nurses, visitors, and even the patient may perceive the indication thatthe sensor 200 has expired.

According to the foregoing embodiment where every second that theoximeter 105 sends drive pulses to the sensor 200, the seventeen-bitNVRAM 305 is incremented, the MSB of the NVRAM 305 will set after131,072 seconds, or, one day, twelve hours, twenty-four minutes andthirty two-seconds. In other words, according to this embodiment, theuseful life of the sensor 200 expires after the sensor 200 has receiveddrive pulses for a combined total of the foregoing time.

A skilled artisan will understand that a wide number of differing logicmechanisms may be employed in the foregoing embodiment. For example,employing different sized counters 300 or NVRAMs 305 will adjust thepredetermined expiration time. Moreover, the counter 300 mayadvantageously divide by more than one thousand, thereby furtherreducing the capacity requirements of the NVRAM 305. Also, the timer 205may advantageously comprise a non-volatile counter that has internalregisters that retain their values when the power is turned off. Suchnon-volatile counters are available, for example, from DallasSemiconductor Corporation of Dallas, Tex. These non-volatile countersmay include, for example, Dallas Semiconductor's DS1602 or DS1603. Inthe foregoing embodiments employing a non-volatile counter, the adder304 and the counter 300 may not be needed.

A skilled artisan will also understand that the sensor 200 mayadvantageously employ a wide variety of differing timers 205 anddiffering sensor life indicators 210. Moreover, the choice mayadvantageously coincide with particular types of the sensor 200. Forexample, a purely disposable sensor suggests a less costly solution thanthat of the reusable sensor because of manufacturing costs and therelatively short life of the disposable sensor. On the other hand, thecombination sensor may incorporate a more expensive solution into thereusable portion of the electronic circuitry without dramatic costchanges to the disposable portion.

Moreover, a skilled artisan will recognize that the timer 205 mayadvantageously comprise a capacitor that is charged when the sensor 200is connected to the oximeter 105. In such case, the capacitor has knowndischarge characteristics such that the voltage across the capacitor canbe used to measure the useful life of the sensor 200. Also, rather thanusing the pulses of the drive signal, the timer 205 may employ anoscillator configured to trigger at the beginning of sensor use.

Further, the sensor life indicator 210 may include several LEDs ofdiffering colors, such as green and red, to indicate whether the sensor200 has expired. The sensor life indicator 210 may comprise anincandescent light, an audio or vibrational alarm, a digital or LCDdisplay, or other sensible indicia. Moreover, the sensor life indicator210 may include a blocking signal for automatically terminating thefunctionality of the sensor 200. For example, a logic gate may beadvantageously added to the drive signal such that the logic gate hasthe drive signal as an input and has the output of the timer 205 as theanother. When the output of the timer 205 is a logic level signalingexpiration, the logic gate blocks the drive signal from passing, thusrending the sensor 200 inoperative. The foregoing logic circuit may alsobe used to block the signal transferred through the return signalconnection 150. On the other hand, the blocking signal may also comprisea fuse that once blown, renders the sensor 200 inoperative.

Accordingly, a skilled artisan may perceive a variety of differingdevices to measure the longevity of the sensor 200. Furthermore, thetype of the sensor 200 may provide guidance on which of the wide varietyof devices to use.

FIG. 4 illustrates a block diagram of yet another embodiment of anoximetry system 400 including a sensor life monitoring system 405.According to this embodiment, the sensor life monitoring system 405employs the timer 205 and a return signal 410 to the oximeter 105.Similar to the foregoing embodiment, the timer 205 connects to the driveconnection 135 and uses the pulses of the drive signal to measure theuseful and safe life of the sensor 200. In contrast to the foregoingembodiment, the timer 205 then outputs an incremental count of pulses tothe oximeter 105 via the return signal 410, the cable connector 155, thesensor connector 160, and the patient cable 115. In this embodiment, themicroprocessor 120 of the oximeter 105 receives the incremental countfrom the timer 205 and compares the incremental count with apredetermined amount. If the count is greater than the predeterminedamount, the microprocessor 120 issues an expiration indication of thesensor 200 through the oximeter 105.

A skilled artisan will recognize that the oximeter 105 may issue theexpiration indication through a wide variety of devices including, butnot limited to, those described in relation to the sensor life indicator210 of FIGS. 2-3. Moreover, the oximeter 105 may take advantage of themore costly technology already associated therewith. For example, theoximeter 105 may issue the expiration indication by employing an audioalarm through the speaker 125, a visual alarm through the display 130,or a power-down function where the oximeter 105 is inoperable until thesensor 200 is replaced.

FIG. 5 illustrates a block diagram of yet another embodiment of anoximetry system 500 including a sensor life monitoring system 505.According to this embodiment, the sensor life monitoring system 505employs a reset indicator 510 and the sensor life indicator 210, as anintegral part of the sensor 200. The reset indicator 510 and the sensorlife indicator 210 connect to the oximeter 105 through the cableconnector 155, the sensor connector 160, and the patient cable 115. Alsoaccording to this embodiment, the microprocessor 120 includes a timer515.

According to this embodiment, the microprocessor 120 measures the usefuland safe life of the sensor 200. For example, the microprocessor 120 maytrack the pulses in the drive signal created by the microprocessor 120,or take advantage of a date/time function to measure actual time.Furthermore, the microprocessor 120 employs the reset indicator 510 onthe sensor 200 to indicate whether the sensor 200 is newly attached orhas previously expired. For example, the reset indicator 510 maycomprise a one-bit memory or a fuse technology, wherein the one-bitmemory is set, or the fuse is blown, when the sensor 200 first connectsto the oximeter 105 through the mating of the cable and sensorconnectors, 155 and 160 respectively.

As shown in FIG. 5, the sensor life indicator 210 remains an integralpart of the sensor 200 and, therefore, may advantageously take any ofthe forms discussed above with reference to FIGS. 2 and 3. Preferably,the sensor life indicator 210 comprises the LED 310 of FIG. 3.

FIG. 6 illustrates a flow diagram 600 of the steps taken by themicroprocessor 120 of the oximetry system 500 of FIG. 5, according toone embodiment of the invention. As shown in FIG. 6, the process beginswhen the oximeter 105 is activated to a sensing state by, for example,an operator, in a STEP 603. The oximeter 105 first checks the resetindicator 510, in a STEP 605, to determine whether the sensor 200 hasbeen previously used. If the sensor 200 is new, the microprocessor 120resets the timer 515, in a STEP 610, and sets the reset indicator 510 onthe sensor 200, in a STEP 615. The microprocessor 120 then proceeds withnormal operation, e.g., to output a drive signal to the sensor 200, in aSTEP 620.

On the other hand, if in the STEP 605, the reset indicator 510 indicatesthat the sensor 200 has been previously used, or when the sensor 200 isin normal operation, in the STEP 620, the microprocessor 120 checkswhether the timer 515 indicates the sensor 200 has reached itspredetermined longevity, in a STEP 625. For example, the timer 515 mayadvantageously compare the number of drive pulses to a predeterminednumber to conclude whether the sensor 200 has expired.

If the sensor 200 has not expired, the microprocessor 120 again proceedswith normal operation, in the STEP 620. On the other hand, if the timer515 indicates that the sensor 200 has expired, the microprocessor 120activates the sensor life indicator 210, in a STEP 630, and then theprocess terminates, in a STEP 635.

One having ordinary skill in the art will understand that themicroprocessor 120 may employ an interrupt driven mechanism for thetimer 515. For example, during normal operation, the microprocessor 120may not continually, or periodically, check the timer 515, as in theSTEP 625. Rather, the microprocessor 120 may continually send drivepulses until the timer 515 generates an interrupt that instructs themicroprocessor 120 to activate the sensor life indicator 210. A skilledartisan will appreciate that there are a wide number of mechanisms forgenerating microprocessor interrupts.

FIG. 7 illustrates a block diagram of yet another embodiment of anoximetry system 700 including a sensor life monitoring system 705.According to this embodiment, the oximetry system 700 is similar to thatdescribed in reference to FIG. 5. Like FIG. 5, the microprocessor 120 ofthe oximeter 105 includes the timer 515, or timer-like functions. Also,the sensor life monitoring system 705 advantageously employs the resetindicator 510 to ensure replacement of new sensors when the sensor 200expires. Moreover, like FIG. 4, the oximetry system 700 employs theoximeter 105 to provide an expiration indication once the sensor 200expires.

Thus, according to one embodiment, the microprocessor 120 of theoximeter 105 checks the reset indicator 510 to ensure the sensor 200 hasnot previously been used. Then, the microprocessor 120 drives the LEDnetwork 140 and tracks the timing functions. When the predeterminednumber of drive pulses is reached, the microprocessor 120 employsvarious mechanisms on the oximeter 105 to generate the expirationindication. For example, the microprocessor 120 may use the speaker 125or the display 130, even power down the oximeter 105, or the like, tocreate the expiration indication.

FIG. 8 illustrates a block diagram of yet another embodiment of anoximetry system 800. According to this embodiment, the oximetry system800 includes a sensor life monitoring system 805 having a memory device810. The memory device 810 is preferably a single wire memory devicehaving a unique identifier, such as memory devices commerciallyavailable from companies such as Dallas Semiconductor Corporation. Forexample, Dallas Semiconductor's DS2401 includes a unique, 64-bitidentification number. In this way, the memory device 810 can uniquelyidentify the sensor 200 from all other sensors.

The oximetry system 800 further includes the microprocessor 120 of theoximeter 105 connected to a memory, such as a database 815. According tothe preferred embodiment, the database 815 is stored locally in thememory of the oximeter 105. The oximeter 105 reads the unique identifierfrom the memory device 810 on the sensor 200 and, if necessary, createsa record in the database 815 corresponding to the unique identifier.Then, as the sensor 200 is used, the oximeter 105 accesses the recordcorresponding to the unique identifier so as to update the informationrelating to the longevity of the sensor 200. This information mayadvantageously include timing information, such as a decremented orincremented chronological count. The information may also, oralternatively, include the number of times the sensor 200 has been used,the number of drive signals the sensor 200 has received, or othersimilar methods of determining the amount of use for the particularsensor 200 having the particular unique identifier.

According to this embodiment, when the information stored in thedatabase 815 reaches a predetermined threshold for a particular uniqueidentifier, the oximeter 105 advantageously produces the expirationindication in a similar manner to that described in reference to FIG. 4.For example, the oximeter 105 may issue the expiration indication byemploying an audio alarm through the speaker 125, a visual alarm throughthe display 130, or a power-down function that renders the oximeter 105inoperable. These expiration indications may advantageously continueuntil the sensor 200 having the unique identifier is replaced with onehaving a different unique identifier.

Although the database 815 is described as being stored in memoryassociated with the oximeter 105, the invention is not meant to belimited thereby. Rather, a skilled artisan would recognize that thedatabase 815 may advantageously be stored in a central location, such aremote server connected through a wide number of known technologies,such as a local or wide area network, the Internet, or othercommunications connection. In this way, a monitoring authority, rangingfrom a pair of pulse oximeters, to one or a number of hospitals, to aparticular sensor manufacturer, and the like, can monitor the usefullife of sensors identified through their unique identifier stored in thememory device 810.

As an alternative to, or in addition to, the foregoing embodiment wherethe memory device 810 includes a unique identifier, the memory device810 may include the ability to store data. Again, such memory devicesare commercially available from, for example, Dallas SemiconductorCorporation, and typically allow for read/write access over a singlewire. For example, Dallas Semiconductor's DS2502 has the ability toaccept new data for non-volatile storage.

According to this embodiment, the oximeter 105 reads data stored in thememory device 810 relating to longevity, and updates that data accordingto use. For example, the oximeter 105 may read the memory device 810 ofsensor 200 and determine that the sensor 200 has been in use for oneincrement of time, such as one minute. After the sensor 200 has beenused for another increment of time, such as another minute as measuredby the oximeter 105, the oximeter may write to the memory device 810such that the memory device 810 now reflects that the sensor 200 hasbeen used for two minutes. This periodic read and write to the memorydevice 810 continues until the memory device 810 reflects a longevitymeasurement greater than a predetermined threshold. At that time, theoximeter 105 may advantageously issue the foregoing expirationindication.

A skilled artisan would recognize that a wide variety of timing schemesmay be implemented using the foregoing read/write technique. Forexample, the oximeter 105 may advantageously decrement from apredetermined threshold stored in the memory device 810. On the otherhand, the memory device may store the number of times the sensor 200 hasbeen used, the number of drive signals the sensor 200 has received, orother similar methods of determining the amount of use for theparticular sensor 200.

Moreover, a skilled artisan would recognize that the foregoingembodiments may advantageously be combined such that the memory device810 includes both the unique identifier and the ability to store otherdata. This other data may advantageously include the foregoingread/write timing data, manufacturing data such as sensor type,manufacturing source indication, tolerance levels, operatingcharacteristics, and the like.

Although the foregoing invention has been described in terms of certainpreferred embodiments, other embodiments will be apparent to those ofordinary skill in the art. For example, a skilled artisan will recognizethe distinction in the foregoing embodiments between those componentsdescribed as being integral with the sensor 200, or on-sensorcomponents, and those components described as not being integral withthe sensor 200, or off-sensor components. The on-sensor components mayadvantageously be housed in the disposable, reusable, or combinationsensors. With respect to the combination sensors, the on-sensorcomponents may be advantageously housed in the disposable portion, thereusable portion, or both portions, of the combination sensor.

Further, the off-sensor components may be housed in any of the longerlasting components associated with the oximeter 105. For example, theoff-sensor components may be advantageously located on the sensorconnector 160 or on the patient cable 115 where they are readily seen,heard, or felt by the operator or patient.

Moreover, the foregoing embodiments incorporating the memory device 810of FIG. 8 may advantageously be combined with those embodimentsdescribing the sensor life indicator 210 housed on the sensor 200. Insuch embodiment, the oximeter 105 may advantageously provide theexpiration indication to the sensor life indicator 210 when the oximeter105 determines that the sensor 200 had expired.

Additionally, other combinations, omissions, substitutions andmodifications will be apparent to the skilled artisan in view of thedisclosure herein. Accordingly, the present invention is not intended tobe limited by the reaction of the preferred embodiments, but is to bedefined by reference to the appended claims.

1. A quality control method configured to provide a caregiver anindication that reusable portions of medical products have not beenoverused, the method comprising: connecting a medical sensor to amonitor, the medical sensor comprising at least some reusuable portionsincluding at least one electronic component, said at least oneelectronic component comprising an identifier; accessing said identifierto electronically determine a cumulative measure based on an amount ofuse of said reusable portions, said cumulative measure including atleast one quantitative indication of actual use responsive to at leasteach transition of a medical sensor drive signal; and activating anindicator alerting a caregiver when said cumulative measure compares toan intended threshold amount of cumulative use in a predeterminedmanner, said intended threshold amount of said cumulative usecorresponding at least in part with a determination of longevity of saidat least some reusable portions of said medical sensor.
 2. The qualitycontrol method of claim 1, comprising associating said cumulativemeasure with said identifier.
 3. The quality control method of claim 2,comprising configuring said monitor to determine a cumulative measurefor each of a plurality of sensors and tracking said cumulative measurefor each sensor by its associated identifier.
 4. The quality controlmethod of claim 3, wherein said connecting said medical sensor comprisesconnecting said medical sensor where said identifier comprises a uniqueidentifier.
 5. The quality control method of claim 1, wherein saidconnecting said medical sensor comprises connecting said medical sensorwhere said identifier comprises a unique identifier.
 6. The qualitycontrol method of claim 1, wherein said connecting said medical sensorcomprises connecting an optical sensor.
 7. A system for preventingoveruse of medical products, the system comprising: a medical sensorincluding at least some reusuable portions, said reusable portionsincluding an identifier; a physiological monitor configured tocommunicate with said medical sensor to process with a signal processorsignals from said medical sensor and determine from said signals outputmeasurements for one or more physiological parameters of a monitoredpatient, said monitor additionally configured to access said identifierto determine a cumulative measure based on an amount of use of saidreusable portions, said cumulative measure including at least onequantitative indication of actual use at least responsive to transitionsof a medical sensor drive signal during operation, wherein said monitoris also configured to alert a caregiver when said cumulative measurecompares to an intended threshold amount of cumulative use in apredetermined manner, said intended threshold amount of said cumulativeuse corresponding at least in part with a determination of longevity ofsaid at least some reusable portions of said medical sensor.
 8. Thesystem of claim 7, wherein said identifier comprises a uniqueidentifier.
 9. The system of claim 7, wherein said medical sensorcomprises an optical sensor.
 10. An electronic memory device storingcumulative use data associated with a reusable component of a medicaldevice, said medical device having a period of safe use as measured atleast in part by transitions of medical device drive signals duringoperation, said memory storing a unique identifier usable to identifysaid reusable component to determine whether said reusable component hasbeen used within a predetermined amount of said period of safe use andto determine whether to alert a caregiver when said use of said reusablecomponent exceeds said predetermined amount in order for use of saidreusable component to be discontinued.
 11. A patient monitor comprisingsaid electronic memory of claim
 10. 12. A sensor comprising said memoryof claim
 10. 13. The sensor of claim 12, comprising an optical sensor.